Well, to be honest I have mixed opinions about fighting games. The issues with them generally come down to balance. Relative skill is also a difficult thing to argue because a lot of it has to do with timing as much as anything, it's not always about what you do, but when you do it. For example when "Soul Calibur IV" first game out, I was able to decimate many opponents with just a couple of basic moves by using Sophitia due to timing and movement, yet I got numerous complaints about how I was "unsportsmanlike", and it has a lot ot do with why I don't really do fighting games online much anymore given the inabillity of automated systems to prevent your player rating/rep from being damaged by people who are QQing because they lost, you broke their win streak, or they really just don't want to risk running into a player who they know can beat them.
As far as my favorite series goes, I'm not sure if I really have one, pretty much all of the big series have their ups and downs and some installments are far better than others.
As far as changing the format and doing new things with them goes, I don't really see the point, you alter things to much and they won't be fighting games anymore, which is something a lot of people making criticisms of game generes (and there are people who criticize every genere) seem to miss. For the most part the way fighting games are set up works perfectly for what they are intended to do.
That said, I do think they need to put more attention into balancing fighting games, not just in what characters can do, but in terms of "motions to results". See, one of the issues I tend to have with such games is that some of the most powerful moves are the easiest to perform in many cases. Argueing that something can be countered is pointless if it say takes 6 inputs for the counter to a 3 input move. The more inputs the more chances for a mistake and the less effective a move becomes, as well as it's practicality as a counter. Arguements about what a highly skilled player might be able to do (perfect all the time) don't really apply to your more typical run of players. A good exmaple of this would be the "shoto fireballs" of characters like Ken and Ryu, they are very versatile, spammable attacks,
that can get some pretty impressive results even in the hands of a relative scrub. I've been of the opinion for a while that a move like that should be more difficult to perform given it's power and versatility as one example.... as someone who has both exploited it, and faced it.
I'm rambling of course, but this thread got me thinking again, even if it's nothing I haven't said before.
I'm also surprised that SNK isn't on the list, given that SNK has one of the longest running stable of fighting game titles ever, and they keep getting recycled, ported, and remade. I wouldn't quite rank any of them as my favorites, but I do think that the SNK fighters should be considered right alongside the likes of Street Fighter and Mortal Kombat.